This document provides information about system administration in Linux, including:
1. It discusses important administrative directories like /etc, /sbin, and /usr/sbin that contain configuration files and commands for system management.
2. It outlines some common ongoing tasks for a Linux system administrator like configuring hardware, managing file systems and disk space, and monitoring system performance.
3. It also covers security tools like SELinux that can help enforce access controls and security policies on a Linux system.
With the introduction of CentOS Stream, it is now possible to contribute to CentOS directly. This talk will go over Facebook's experience working with CentOS (the distro, the project, the community), growing from consumer, to contributor, to founding member of the new Hyperscale SIG, which strives to facilitate collaboration around large-scale CentOS deployments.
With the introduction of CentOS Stream, it is now possible to contribute to CentOS directly. This talk will go over Facebook's experience working with CentOS (the distro, the project, the community), growing from consumer, to contributor, to founding member of the new Hyperscale SIG, which strives to facilitate collaboration around large-scale CentOS deployments.
This lecture discusses the concept of Multi-User support in Linux. It discusses how Linux protects user files and resources from other user unauthorized access. It also shows how to share resources and files among users, how to add/del users and groups.
Check the other Lectures and courses in
http://Linux4EnbeddedSystems.com
or Follow our Facebook Group at
- Facebook: @LinuxforEmbeddedSystems
Lecturer Profile:
- https://www.linkedin.com/in/ahmedelarabawy
Red Hat Enterprise Linux (RHEL) is a Linux-based operating system from Red Hat designed for businesses. RHEL can work on desktops, on servers, in hyper visors or in the cloud. Red Hat and its community-supported counterpart, Fedora, are among the most widely used Linux distributions in the world.
Linux-training-for-beginners-in-mumbaiUnmesh Baile
Vibrant Technologies is headquarted in Mumbai,India.We are the best Linux training provider in Navi Mumbai who provides Live Projects to students.We provide Corporate Training also.We are Best Linux classes in Mumbai according to our students and corporates
Twitter for Consumer Businesses: Overview of Twitter Business Uses & TrendsAdam Schoenfeld
An overview of Twitter for B2C businesses I recently presented for a group of venture capitalists. The deck touches on the following points:
1. Why do consumer businesses care about Twitter?
2. How is Twitter being used - high level?
3. How is Twitter being used for customer service and market - specifics
4. Take Aways
5. Trends to watch
This lecture discusses the concept of Multi-User support in Linux. It discusses how Linux protects user files and resources from other user unauthorized access. It also shows how to share resources and files among users, how to add/del users and groups.
Check the other Lectures and courses in
http://Linux4EnbeddedSystems.com
or Follow our Facebook Group at
- Facebook: @LinuxforEmbeddedSystems
Lecturer Profile:
- https://www.linkedin.com/in/ahmedelarabawy
Red Hat Enterprise Linux (RHEL) is a Linux-based operating system from Red Hat designed for businesses. RHEL can work on desktops, on servers, in hyper visors or in the cloud. Red Hat and its community-supported counterpart, Fedora, are among the most widely used Linux distributions in the world.
Linux-training-for-beginners-in-mumbaiUnmesh Baile
Vibrant Technologies is headquarted in Mumbai,India.We are the best Linux training provider in Navi Mumbai who provides Live Projects to students.We provide Corporate Training also.We are Best Linux classes in Mumbai according to our students and corporates
Twitter for Consumer Businesses: Overview of Twitter Business Uses & TrendsAdam Schoenfeld
An overview of Twitter for B2C businesses I recently presented for a group of venture capitalists. The deck touches on the following points:
1. Why do consumer businesses care about Twitter?
2. How is Twitter being used - high level?
3. How is Twitter being used for customer service and market - specifics
4. Take Aways
5. Trends to watch
Our lives are changing at an unprecedented pace. Transformational shifts in our economic, environmental, geopolitical, societal and technological systems offer unparalleled opportunities, but the interconnections among them also imply enhanced systemic risks. Stakeholders from across business, government and civil society face an evolving imperative in understanding and managing emerging global risks which, by definition, respect no national boundaries.
In 2015, the Aon Global Risk Management Survey revealed how increasing competition remained at the top of the industry’s list of concerns, but the potential for damage to brand and reputation is now second, having risen up from seventh place in the previous survey.
Like any responsible supplier, we know that the answer to delivering a good service is to ensure our customers are fully furnished with the facts that may influence their buying decisions. In this report, we consider how these factors translate into the risk profile of UK retail and how they may influence insurers to underwrite them at a good price, or lower, than last time around
For a company like Aon, sectors like food and drink manufacturing are our lifeblood. The industry employs over 400,000 people in the UK, accounts for more than £80bn in annual turnover and we are proud to work with many of the sector’s leading companies in the UK and across the world.
Now joining us for the third year in a row, Ash will provide a further ‘digital dear diary’ update, focusing specifically on his team’s work to influence change to build a truly digital culture across the organisation.
In June 2013, Ash Roots spoke at the Digital Summit just a few months into his role as Director of Digital at Direct Line Group. Brought in to lead a digital transformation at the major insurer, he explained what he’d learned in his early weeks and months… what was working and what wasn’t… how he was trying to build capability and what he saw coming down the road. One year later, Ash reprised his role with an update. How had the last year gone? What progress had been made and what led to that progress? Did things really pan out the way he thought and if not, what got in the way and how did he tackle it?
Deep Dive Into How To Monitor MySQL or MariaDB Galera Cluster / Percona XtraD...Severalnines
MySQL provides hundreds of status counters, but how do you make sense of all that monitoring data?
If you’re in Operations and your job is to monitor the health of MySQL/MariaDB Galera Cluster or Percona XtraDB Cluster, then this webinar is for you. Setting up a Galera Cluster is fairly straightforward, but keeping it in a good shape and knowing what to look for when it’s having production issues can be a challenge.
Status counters can be tricky to read …
Which of them are more important than others?
How do you find your way in a labyrinth of different variables?
Which of them can make a significant difference?
How might a host’s health impact MySQL performance?
How to identify problematic nodes in your cluster?
To find out more, read these webinar slides (or watch the replay).
Our colleague Krzysztof Książek provided a deep-dive session on what to monitor in Galera Cluster for MySQL & MariaDB. Krzysztof is a MySQL DBA with experience in managing complex database environments for companies like Zendesk, Chegg, Pinterest and Flipboard.
Amongst other things, Krzysztof discussed why having a good monitoring system is a must, covering the following topics:
Galera monitoring
• cluster status
• flow control
Host metrics and their impact on MySQL
• CPU
• memory
• I/O
InnoDB metrics
• CPU-related
• I/O-related
CompTIA Linux+ Powered by LPI certifies foundational skills and knowledge of Linux. With Linux being the central operating system for much of the world’s IT infrastructure, Linux+ is an essential credential for individuals working in IT, especially those on the path of a Web and software development career. With CompTIA’s Linux+ Powered by LPI certification, you’ll acquire the fundamental skills and knowledge you need to successfully configure, manage and troubleshoot Linux systems. Recommended experience for this certification includes CompTIA A+, CompTIA Network+ and 12 months of Linux admin experience. No prerequisites required.
In February, 2016 I had the privilege of working with employees of STARR Computers on a course to orient them to Linux. The course was delivered over a series of 90-120 minute sessions. It was designed so that
This is a compilation of the slides which were used. There were some other resources which were shared. There were practice exercises which were designed to reinforce some concepts.
Check http://churchroadman.blogspot.com/2016/04/basic-orientation-to-linux-course.html for some other details.
Elevating Tactical DDD Patterns Through Object CalisthenicsDorra BARTAGUIZ
After immersing yourself in the blue book and its red counterpart, attending DDD-focused conferences, and applying tactical patterns, you're left with a crucial question: How do I ensure my design is effective? Tactical patterns within Domain-Driven Design (DDD) serve as guiding principles for creating clear and manageable domain models. However, achieving success with these patterns requires additional guidance. Interestingly, we've observed that a set of constraints initially designed for training purposes remarkably aligns with effective pattern implementation, offering a more ‘mechanical’ approach. Let's explore together how Object Calisthenics can elevate the design of your tactical DDD patterns, offering concrete help for those venturing into DDD for the first time!
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
Have you ever wanted a Ruby client API to communicate with your web service? Smithy is a protocol-agnostic language for defining services and SDKs. Smithy Ruby is an implementation of Smithy that generates a Ruby SDK using a Smithy model. In this talk, we will explore Smithy and Smithy Ruby to learn how to generate custom feature-rich SDKs that can communicate with any web service, such as a Rails JSON API.
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
2. Administration
• Becoming the Super User (the su Command)
• Administrative GUI Tools
• Many commands are intended only for root.
• /sbin — This contains commands for modifying your disk
partitions (such as fdisk), changing boot procedures
(grub), and changing system states (init).
• /usr/sbin —This contains commands for managing user
accounts (such as useradd) and checking network traffic
(wireshark). Commands that run as daemon processes
are also contained in this directory. (Look for commands
that end in d, such as sshd, pppd, and crond.)
3. Administrative Config Files
• Almost everything you set up for your
particular computer — user accounts,
network addresses, or GUI preferences —
is stored in plaintext files.
4. $HOME
• All users store information in their home
directories that directs how their login
accounts behave. Most configuration files
in $HOME begin with a dot (.), so they
don’t appear as a user’s directory when
you use a standard ls command (you
need to type ls –a to see them)
5. /etc
• adjtime—Holds data to adjust the hardware clock (see the hwclock
man page).
• aliases —Can contain distribution lists used by the Linux mail
service.
• bashrc—Sets system-wide defaults for bash shell users. (By
default, it sets the shell prompt to include the current user name,
hostname, current directory, and other values.)
• cdrecord.conf —Contains defaults used for recording CDs.
• crontab—Sets cron environment and times for running automated
tasks.
• csh.cshrc (or cshrc)—Sets system-wide defaults for csh (C shell)
users.
• dovecot—Contains information needed to support the dovecot
IMAPv4/POP3 mail service.
6. /etc
• esd.conf —Sets options used by the
Enlightenment Sound Daemon to mix multiple
audio streams into a single audio output.
• exports—Contains a list of local directories that
are available to be shared by remote computers
using the Network File System (NFS).
• fstab—Identifies the devices for common
storage media (hard disk, floppy, CD-ROM, etc.)
and locations where they are mounted in the
Linux system. This is used by the mount
command to choose which file systems to
mount.
7. /etc
• group—Identifies group names and group IDs (GIDs) that are defined in the
systems. Group permissions in Linux are defined by the second of three
sets of rwx (Read, Write, Execute) bits associated with each file and
directory.
• gshadow—Contains shadow passwords for groups.
• host.conf — Sets the locations in which domain names (e.g., redhat.com)
are searched for on TCP/IP networks (such as the Internet). By default, the
local hosts file is searched, then any nameserver entries in resolv.conf.
• hosts—Contains IP addresses and hostnames that you can reach from
your computer. (Usually this file is used just to store names of computers on
your LAN or small private network.)
• hosts.allow—Lists host computers that are allowed to use certain TCP/IP
services from the local computer.
• hosts.deny—Lists host computers that are not allowed to use certain
TCP/IP services from the local computer (doesn’t exist by default).
8. /etc
• inittab—Contains information that defines which
programs start and stop when Linux boots, shuts down,
or goes into different states (runlevels) in between. This
is the most basic configuration file for starting Linux.
• issue—Contains the lines that are displayed when a
terminal is ready to let you log in to your system from a
local terminal, or the console in text mode.
• issue.net— Contains login lines that are displayed to
users who try to log in to the Linux system from a
computer on the network using the telnet service.
• mail.rc —Sets system-wide parameters associated with
using mail.
• man.config—Used by the man command to determine
the default path to the location of man pages.
9. /etc
• modprobe.conf — Contains aliases and options
related to loadable kernel modules
• used by your computer.
• mtab—Contains a list of file systems that are
currently mounted.
• mtools.conf —Contains settings used by DOS
tools in Linux.
• named.conf —Contains DNS settings if you are
running your own DNS server.
• ntp.conf —Includes information needed to run
the Network Time Protocol (NTP).
10. /etc
• passwd— Stores account information for all valid users
for the system. Also includes other information, such as
the home directory and default shell.
• printcap—Contains definitions for the printers configured
for your computer.
• profile —Sets system-wide environment and start-up
programs for all users. This file is read when the user
logs in.
• protocols—Sets protocol numbers and names for a
variety of Internet services.
• redhat-release—Contains a string identifying the current
CentOS release.
11. /etc
• resolv.conf — Identifies the locations of DNS name
server computers that are used by TCP/IP to translate
Internet host.domain names into IP addresses.
• rpc —Defines remote procedure call names and
numbers.
• services— Defines TCP/IP services and their port
assignments.
• shadow—Contains encrypted passwords for users who
are defined in the passwd file. (This is viewed as a more
secure way to store passwords than the original
encrypted password in the passwd file. The passwd file
needs to be publicly readable, whereas the shadow file
can be unreadable by all but the root user.)
12. /etc
• shells —Lists the shell command-line interpreters (bash, sh, csh,
etc.) that are available on the system, as well as their locations.
• sudoers—Sets commands that can be run by users, who may not
otherwise have permission to run the command, using the sudo
command. In particular, this file is used to provide selected users
with root permission.
• syslog.conf —Defines what logging messages are gathered by the
syslogd daemon and what files they are stored in. (Typically, log
messages are stored in files contained in the /var/log directory.)
• termcap—Lists definitions for character terminals, so that
character-based applications know what features are supported by
a given terminal. Graphical terminals and applications have made
this file obsolete to most people. (Termcap was the BSD UNIX way
of storing terminal information; UNIX System V used definitions in
/usr/share/terminfo files.)
13. /etc/X11
• Contains subdirectories that each contain
system-wide configuration files used by X
and different X window managers
available for Linux. The xorg.conf file
(which makes your computer and monitor
usable with X) and configuration
directories containing files used by xdm
and xinit to start X are in here.
14. /etc
• /etc/amanda —Contains files and directories that
allow the amanda facility to do network backups
of other Linux and UNIX systems.
• /etc/cron* — Directories in this set contain files
that define how the crond utility runs applications
on a daily (cron.daily), hourly (cron.hourly),
monthly (cron.monthly), or weekly (cron.weekly)
schedule.
• /etc/cups —Contains files that are used to
configure the CUPS printing service.
15. /etc
• /etc/default —Contains files that set default values for
various utilities. For example, the file for the useradd
command defines the default group number, home
directory, password expiration date, shell, and skeleton
directory (/etc/skel) that are used when creating a new
user account.
• /etc/httpd —Contains a variety of files used to configure
the behavior of your Apache Web server (specifically,
the httpd daemon process).
• /etc/init.d — Contains links to the run-level scripts. These
scripts are linked from files in the /etc/rc?.d directories to
have each service associated with a script started or
stopped for the particular run level. The ? is replaced by
the run-level number (0 through 6).
16. /etc
• /etc/mail —Contains files used to configure your
sendmail mail service.
• /etc/pcmcia — Contains configuration files that allow you
to have a variety of PCMCIA cards configured for your
computer. (PCMCIA slots are those openings on your
laptop that allow you to have credit card–sized cards
attached to your computer. You can attach such devices
as modems and external CD-ROMs.)
• /etc/postfix —Contains configuration files for the postfix
mail transport agent.
• /etc/ppp —Contains several configuration files used to
set up Point-to-Point protocol (so that you can have your
computer dial out to the Internet).
17. /etc
• /etc/rc?.d —There is a separate rc?.d directory for each valid
system state: rc0.d (shutdown state), rc1.d (single-user state), rc2.d
(multiuser state), rc3.d (multiuser plus networking state), rc4.d
(user-defined state), rc5.d (multiuser, networking, plus GUI login
state), and rc6.d (reboot state).
• /etc/security —Contains files that set a variety of default security
conditions for your computer. These files are part of the pam
(pluggable authentication modules) package.
• /etc/skel —Any files contained in this directory are automatically
copied to a user’s home directory when that user is added to the
system. By default, most of these files are dot (.) files, such as .kde
(a directory for setting KDE desktop defaults) and .bashrc (for
setting default values used with the bash shell).
18. /etc
• /etc/squid —Contains configuration files for the Squid proxy caching server.
• /etc/sysconfig —Contains important system configuration files that are
created and
• maintained by various system services (including iptables, samba, and most
networking services).
• /etc/uucp —Contains configuration files used with Taylor UUCP (a
nonstandard version of the uucp facility that is used to create modem, direct
line, and other serial connections with other computers).
• /etc/vsftpd —Contains configuration files used to set up the vsftpd FTP
server.
• /etc/xinetd.d —Contains a set of files, each of which defines a network
service that the xinetd daemon listens for on a particular port. When the
xinetd daemon process receives a request for a service, it uses the
information in these files to determine which daemon processes to start to
handle the request.
19. Administrative Log Files
• keep track of itself.
• monitor your system to see if people are
trying to access your computer illegally.
• General system logging is done by
syslogd.
• As root user, you can view log files with
the less command or watch messages as
they enter log file using the tail command
(tail -f /var/log/messages).
20. Ongoing
job as a Linux system administrator
• Configuring Hardware —Often when you
add hardware to your CentOS computer,
that hardware will be automatically
detected and configured by tools. can use
commands such as lsmod, modprobe,
insmod, and rmmod to configure the right
modules to get the hardware working.
• To see what HAL knows about your
system, run the lshal command:
21. Ongoing
job as a Linux system administrator
• Managing File Systems and Disk Space
—You must keep track of the disk space
being consumed, especially if your
CentOS system is shared by multiple
users. At some point, you may need to
add a hard disk or track down what is
eating up your disk space (you can use
commands like find, du, and df to do
this).
22. Ongoing
job as a Linux system administrator
• Monitoring System Performance —You
may have a runaway process on your
system, or you may just be experiencing
slow performance. Tools that come with
CentOS can help you determine how
much of your CPU and memory are being
consumed.
23. Mounting/umount Removable
Media
• CD-ROM—If you are mounting a CD-ROM
that is in the standard ISO 9960 format (as
most software CD-ROMs are), you can
mount that CD-ROM by placing it in your
CD-ROM drive and typing the following:
• # mount /mnt/cdrom
• Floppy Disk
• # mount /mnt/floppy
24. Checking System Space
• Checking Disk Space with Disk Usage
Analyzer
• Displaying System Space with df
• To produce output in a more human-
readable form, use the -h option as
follows: $ df -h
25. Checking Disk Usage with du
• The du command is a good way to check
how much space is being used by a
particular user (du /home/user1)
• To make the output more friendly (in
kilobytes, megabytes, and gigabytes), use
the –h
• $ du -h /home/jake
26. Watch Computer Usage with
System Monitor
• System Monitor graphically displays your
system’s CPU and memory usage.
• Monitoring CPU Usage with top
• By adding the -S option to top, you can
have the display show you the cumulative
CPU time that the process
27. Using Security Enhanced Linux
• When you first install CentOS, you have the
opportunity to enable or disable SELinux.
• Targeted policies focus on services with
vulnerable daemon processes
• Targeted policies limit the impact that an attack
on the following services can have on your
server as a whole: Apache (Web server), Samba
(Windows file and print sharing), FTP (file
transfer protocol), NFS (network file system),
and others
28. Policies in SELinux
• Enforcing —The current SELinux policy is
turned on and its policies are enforced.
• Permissive —The current SELinux policy is on,
but not enforced (so you only see warning
messages describing how the policy would be
enforced).
• Disabled —SELinux is off, so only standard
Linux permissions are enforced (as they always
were on systems not including SELinux).
31. Adding Users with useradd
• # useradd -c "Robert Jones" -m robert
• -c "comment“
• -d home_dir
• -e expire_date
• -g group
• -m Automatically create the user’s home
directory
• -p passwd
• # passwd robert
32. Adding Users with User Manager
• A graphical window for adding, changing,
and deleting user accounts, you can use
the User Manager window.
33. Adding User Accounts to Servers
• To prevent a remote user from logging in
and accessing a shell via ssh or another
login service, you can set the default shell
for a user to nologin.
• # useradd -s /sbin/nologin yason
• A common practice with Web hosting is to
allow a user to place content on the server
• # useradd -s /sbin/nologin -d
/var/www/html webuser
34. Resetting a User’s Password
• # passwd yason
• # chage -M 30 -d 0 yason
• The -M 30 option tells the system to expire
yason’s password every 30 days. The -d 0
option tricks the system into thinking that her
password has not been changed since January
1, 1970.
• Keep in mind that using chage activates
password aging for any account on which it is
used.
35. Modifying User Accounts with
usermod
• # usermod -l mike -c "Mike Barnes" -m
-d /home/mike yason
37. Deleting User Accounts
• Deleting User Accounts with userdel
• # userdel yason
• To wipe out her home directory along with
her account, type this:
• # userdel -r yason
• Deleting User Accounts with User
Manager
38. System Startup and Shutdown
• During system startup, a series of scripts
is run to start the services that you need.
• Service Configuration window.